Stone Dragons have a tough outer covering made of a stone-like material. They eat rocks, using the minerals they contain for nourishment and to keep up their stone outer shell. They rarely move, and are the heaviest of all types of dragons. Although they have wings, indicating flight ability, no one has ever seen a stone dragon flying.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

Obsidian is a vigilant dragon, earning the 'Sentry' part of his name for his tendency to rush to a dragon's aid if they're being bullied. Despite this, Obsidian really isn't very active otherwise and is perfectly content to eat rocks and the occasional gemstone. His lustrous red eyes create a penetrating gaze, but this slow-moving dragon is gentle and mild-mannered. His favorite type of rock to eat is obsidian, but in order to find it in large quantities, he must journey to the outskirts of lava fields, nearly a twenty mile walk. Often, his tamer will go with him and help him to carry back some of the substance. To compensate for the distance, he has trained his enormous wings to carry him in flight, as well as carry his tamer on his back.